Evaluation of sleep quality in patients diagnosed with bipolar disorder and major depression during remission period

Table 1 Descriptive and comparative statistics of the study groups, mean ± SD/n (%)

	Total sample (n = 135)
	Bipolar disorder (n = 45)	Major depressive disorder (n = 45)	Healthy controls (n = 45)	χ2/F	P value4	Effect size5	P value6	P value7	P value8
Age1	42.62 ± 10.39	42.77 ± 10.84	41.77 ± 9.53	0.123	0.884
Education (years)1	9.37 ± 4.09	8.86 ± 4.03	9.88 ± 3.43	0.786	0.458
Gender (female)	27 (60.0)	28 (62.2)	28 (62.2)	0.063	0.969
Body mass index2	31.35 ± 5.79	30.22 ± 5.43	27.73 ± 5.33	4.275	0.003	0.070	1.0	0.008	0.116
Unemployed or irregular work	34 (75.6)	20 (44.1)	7 (15.6)	32.718	< 0.001	0.492	BD > MDB, BD > HC, MDB > HC
Single or no partner	15 (33.3)	10 (22.2)	10 (22.2)	1.929	0.381
Smoker (yes)	23 (51.1)	28 (62.2)	28 (62.2)	1.526	0.466
Lifetime AUD/SUD	5 (11.1)	5 (11.1)	1 (2.2)	19.197	0.205
PSQI total3	7.84 ± 3.10	7.22 ± 3.15	4.64 ± 0.82	8.913	< 0.001	0.200	0.891	< 0.001	< 0.001
Subjective sleep quality3	0.82 ± 0.53	0.82 ± 0.49	0.97 ± 0.14	1.684	0.140
Sleep latency	1.84 ± 1.16	1.84 ± 1.12	1.02 ± 0.33	10.790	< 0.001	0.143	1.0	< 0.001	< 0.001
Sleep duration	0.33 ± 0.73	0.20 ± 0.58	0.91 ± 0.35	22.497	< 0.001	0.258	1.0	< 0.001	< 0.001
Habitual sleep efficiency3	0.64 ± 0.74	0.42 ± 0.65	0.04 ± 0.20	10.915	< 0.001	0.145	0.239	< 0.001	0.011
Sleep disturbances	1.35 ± 0.80	1.28 ± 0.78	1.0 ± 0.36	1.435	0.242
Use of sleep medication3	2.06 ± 1.40	1.82 ± 1.45	0.11 ± 0.31	39.128	< 0.001	0.378	0.763	< 0.001	< 0.001
Daytime drowsiness	0.77 ± 1.14	0.82 ± 1.11	0.46 ± 0.50	0.877	0.419
ISI3	4.95 ± 4.26	3.02 ± 2.95	0.60 ± 1.26	19.207	< 0.001	0.229	0.015	< 0.001	0.002
PSQI total cut-off > 5	34 (75.6)	26 (57.8)	4 (8.9)	43.019	< 0.001	0.565	BD > HC, MDD > HC
GAF3	71.66 ± 11.39	78.46 ± 7.76	88.82 ± 3.83	42.681	< 0.001	0.398	< 0.001	< 0.001	< 0.001

¹Post hoc comparisons were conducted using the least significant difference method following a one-way ANOVA.

²Pairwise comparisons are based on ANCOVA using estimated marginal means, adjusted for covariates (age and gender) with the Bonferroni method for multiple comparisons.

³Pairwise comparisons are based on ANCOVA using estimated marginal means, adjusted for covariates (age, body mass index and gender) with the Bonferroni method for multiple comparisons.

⁴Bipolar disorder, major depressive disorder vs healthy control.

⁵Effect sizes were reported as partial eta squared (ANCOVA) and Cramer’s V (χ²).

⁶Bipolar disorder vs major depressive disorder.

⁷Bipolar disorder vs healthy control.

⁸Major depressive disorder vs healthy control.

AUD: Alcohol use disorder; SUD: Non-alcohol substance use disorder; PSQI: Pittsburgh Sleep Quality Index; ISI: Insomnia Severity Index; GAF: Global Assessment of Functioning; BD: Bipolar disorder; MDD: Major depressive disorder; HC: Healthy control.

Table 2 Correlation analysis of sociodemographic data and clinical characteristics

Correlation coefficient	Age1	Education1	Female2	BMI1	Irregular work2	Smoker2	ISI1	GAF1
PSQI total	0.000	-0.005	0.131	0.2073	0.1903	-0.2494	0.7104	-0.4184
ISI	-0.036	-0.075	0.051	0.1963	0.1863	-0.1923	1	-0.4014
GAF	-0.059	0.075	-0.036	-0.2384	-0.3384	-0.040	-0.4014	1

¹Pearson correlation coefficient.

²Spearman’s rank correlation coefficient.

³The correlation is significant (two-tailed) at the 0.05 Level.

⁴Correlation is significant at the 0.01 Level (two-tailed).

PSQI: Pittsburgh Sleep Quality Index; ISI: Insomnia Severity Index; GAF: Global Assessment of Functioning; BMI: Body mass index.

Table 3 Stepwise multivariate regression analysis of factors affecting sleep quality

Variable	β	Significance	95%CI (for β)	VIF
Pittsburgh sleep quality index1
Constant	8.454	< 0.001	5.509-11.400	N/A
Insomnia severity index	0.535	< 0.001	0.428-0.641	1.192
Global functioning	-0.043	0.017	-0.078 to -0.008	1.192

¹A forward stepwise linear regression analysis was conducted. The final model achieved F (3,132) = 73.179, P < 0.001, with an R² of 0.526 and an adjusted R² of 0.519, variables excluded from the model include work status and body mass index.

CI: Confidence interval; VIF: Variance inflation factor; N/A: Not applicable.